It is well-known in the medical arts that constant pressure on a bone fracture speeds healing. As such, orthopedic physicians typically insert one or more screws in the area of the fracture in order to assert constant pressure on the bone fracture. However, the insertion of existing screws through or around fractures has disadvantages. For example, the entire process is very time-consuming because inserting a regular screw usually involves multiple steps such as drilling the pilot hole, measuring the relevant distances to determine the appropriate screw selection, tapping the hole to establish threads and screwing the screw into the hole. Moreover, when using a bone screw, the process usually includes even more steps such as drilling through the near cortex to establish the guiding hole (e.g., 3.5 mm), placing the drill guide in the proper location, drilling through the far cortex (e.g., 2.5 mm), measuring the distance to determine the appropriate screw selection, tapping the hole to establish threads and rotating the screw into the hole, thereby attempting to compress the fracture. Again, each step and the entire process is very time-consuming.
In addition to the length and complexity of the process, the prior art system also typically includes inadequate components. For example, in poor bone, prior art screws often loose their grip and strip out of the bone. Currently available bone screws also typically provide only one side of cortex fixation and are generally not suited for percutaneous surgery. Moreover, when placing the screws in the bone, the physician may not accurately set the screw into the distal hole or may miss the distal hole completely, thereby resulting in the screw stripping the threads or breaking the bone.
Furthermore, the location and extent of most every fracture is unique, so different screws are often needed for each fracture. Because the physician typically is unable to accurately determine the type or size of screw needed until the physician enters the bone and measures the appropriate screw placement, operating facilities need to store and make available large inventories of screws. Particularly, screws usually range in length from about 10 mm to about 75 mm with available screw sizes limited to every 2 mm there between. Moreover, for each size of screw, the screws may be either a cancellous or cortical type, and for each size and type of screw, the screw may include one of three different pitches. Accordingly, a screw set typically exceeds one hundred screws. Furthermore, if cannulated screws are desired, another entire screw set of over one hundred additional screws is often needed. Moreover, each time a screw from a screw set is utilized in a procedure, a replacement screw is typically obtained to complete the set. As such, inventory management of screws is a very large problem for many operating facilities. A need exists for a lagwire system which simplifies and expedites the process for the fixation of bone fractures, while minimizing the number of components needed in the process.
Additionally, in hip fractures (e.g. femoral neck fracture), the non-union rate is about 25-30%. Certain factors may contribute to the non-union rate in fractures such as, for example, poor blood supply and age of patient. However, an important factor for the non-union rate in fractures is micro-motion. Micro-motion of the hip bones is typically caused by the natural movements of the patient while the patient is walking, hopping on crutches, twisting and the like. Such micro-motion has an affect on the bone screw in that the micro-motion often causes the bone screw to slide within the bone, thereby disrupting the bone union. The bone union is disrupted because the union loses its fixed compression and fracture interface is decompressed.
Another concern with bone screws is that the head of bone screw often protrudes out of the bone surface over time. In particular, when a bone fracture is set with a bone screw, the bone screw typically does not completely compress the bone fragments together. As such, after the patient stands and a weight bearing force is applied against the bone fragments (or any other compressive forces applied to the bone fragments), the fragments are further compressed. The further compression of the bone fragments results in the head of the bone screw (which was previously flush with the outside surface of the bone) protruding outside from the surface of the bone. In some cases, the head of the bone screw may protrude about 1 cm which may result in pain and/or the need for additional surgery. A need exists for a device and method for maintaining the initial and subsequent compression of a bone fracture to increase the union rate of the bone fracture.